For robots of human and animal types, attention has in recent years been drawn to active senses of vision and audition. A sense by a sensory device provided in a robot for its vision or audition is made active (active sensory perception) when a portion of the robot such as its head carrying the sensory device is varied in position or orientation as controlled by a drive means in the robot so that the sensory device follows the movement or instantaneous position of a target to be sensed or perceived.
As for active vision, studies have diversely been undertaken using an arrangement in which at least a camera as the sensory device holds its optical axis directed towards a target by being controlled in position by the drive means while permitting itself to perform automatic focusing and zooming in and out relative to the target to take a picture thereof
As for active audition or hearing, at least a microphone as the sensory device may likewise have its facing kept directed towards a target by being controlled in position by the drive mechanism to collect a sound from the target. An inconvenience has been found to occur then with the active audition, however. To wit, with the drive mechanism in operation, the microphone may come to pick up a sound, especially burst noises, emitted from the working drive means. And such sound as a relatively large noise may become mixed with a sound from the target, thereby making it hard to precisely recognize the sound from the target.
And yet, auditory studies made on the limited state that the drive means in the robot is at a halt have been found not to stand especially with the situation that the target is moving and hence unable to give rise to what is called active audition by having the microphone follow the movement of the target.
Yet further, the microphone as the auditory device may come to pick up not only the sound from the drive means but also various sounds of actions generated interior of the robot and noises steadily emitted from its inside, thereby making it hard to provide consummate active audition.
By the way, there has been known an active noise control (ANC) method designed to cancel a noise.
In the ANC method, a microphone is disposed in the vicinity of a noise source to collect noises from the noise source. From the noises, a noise that is the noise which is desirably cancelled at a given area is predicted using an adaptive filter such as an infinite impulse responsive (IIR) or a finite impulse responsive (FIR) filter. In that area, a sound that is opposite in phase to the predicted noise is emitted from a speaker to cancel the same and thereby to cause it to cease to exist.
The ANC method, however, requires data in the past in the noise prediction and is found hard to meet with what is called a bust noise. Further, the use of an adaptive filter in the noise cancellation is found to cause the information on a phase difference between right and left channels to be distorted or even to vanish so that the direction from which a sound is emitted becomes unascertainable.
Furthermore, while the microphone used to collect noises from the noise source should desirably collect noises selectively as much as possible, it is difficult in the robot audition apparatus to collect noises nothing but noises.
Moreover, while the need to entail a time of computation for predicting what the noise is that should desirably be cancelled in a given area requires as a precondition that the speaker be disposed spaced apart from the noise source by more than a certain distance, the robot audition apparatus necessarily reduces the time of computation since an external microphone for collecting an external sound must be disposed adjacent to the inner microphone for collecting noises and makes it impractical to use the ANC method.
It can thus be seen that adopting the ANC method in order to cancel noises generated in the interior of a robot is unsuitable.
With the foregoing taken into account, it is an object of the present invention to provide a robot auditory apparatus and system that can effect active perception by collecting a sound from an outside target with no influence exerted by noises generated inside of the robot such as those emitted from the robot drive means.